Mercury buildup in birds sounds warning for all

London, ON – Higher-than-normal mercury levels may be wiping out the endangered arctic ivory gull, but now Western researchers are warning other species – including humans – are at risk from this deadly neurotoxin.

Mercury levels in arctic ivory gulls have risen almost 50 fold over the past century, said biologist Brian Branfireun, who is associate professor, Canada research chair in environment and sustainability, cross-appointed with Earth Sciences and Geography at Western University. The explosion in those toxins is the likely cause of a plummeting population of the gull, who have only 400-500 breeding pairs left in the world.

The research was recently published in Proceedings of the Royal Society B, the Royal Society’s biological research journal.

Since the 1980s, the population of ivory gulls in Canada has nosedived by more than 80 percent, with a 2004 study finding that the eggs of ivory gulls have the highest concentration of mercury of any arctic seabird, exacerbating the ongoing problem.

“You could make the argument there are plenty of birds. So, why this bird and not another bird?” Branfireun said. “One makes a decision that an organism or species has an intrinsic value for just being. If we extend the intrinsic value of the existence of species, then the ivory gull is just as important as a panda bear, or polar bear, or anything else.”

The ivory gull plays an important role in the coastal arctic ecosystem because they are scavengers. They are like the vultures of the high arctic. This fact, however, is why they are threatened right now – because of what they eat.

As well as consuming fish, ivory gulls scavenge blubber and meat from marine mammal carcasses and it is likely the high concentrations of mercury from these predators, which tend to accumulate at the highest levels, is what is affected the gulls.

Using museum specimens, Branfireun, along with then-University of Saskatchewan postdoctoral fellow Alexander Bond (now with the Royal Society for the Protection of Birds) and Environment Canada’s Keith Hobson, tested the concentration of methyl mercury in the feathers of 80 ivory gulls who lived over the past 130 years. Mercury builds up in feathers where it is trapped and stabilized by processes which produce keratin – which is found in feathers, claws and hair.

They found no evidence of a dietary change in the ivory gulls that could account for the huge increase in mercury. That left humans as the main culprit.

“It went from infinitesimally small and low concentrations to about 5 parts per million, which is quite high for mercury,” said Branfireun.

Mercury, transported long distances from sources in North America, Asia and India, is finding its way to the once isolated and pristine arctic landscape, far from the original sources of human pollution.

Across the Northern Hemisphere, the amount of mercury in the environment has increased due to emission to the atmosphere. It becomes a global pollutant because mercury can also exist as a gas, emitted through coal, in the upper atmosphere, where it circulates for about nine months. Then, it circulates around the entire hemisphere and deposits in the rain, the snow or as dust.

“These birds are basically going to be eliminated from the Canadian arctic,” said Branfireun.

The situation has taken a step in the right direction with the ratification of the Minamata Convention on Mercury, an international treaty designed to protect human health and the environment from emissions and releases of mercury and mercury compounds. But that only impacts the world going forward; we are still paying dearly for the actions of the past.

“Part of the challenge of mercury is, once it’s into the environment, it doesn’t break down,” he said. “It stays there. Once it’s been put into the surface environment – the oceans or soils – it starts grass-hopping around and re-emitting. It is human-derived mercury, but it was deposited in the 1960s and 1970s and is still working its way through soil, vegetation and water.”

The question for Branfireun is: What degree of impact are we comfortable with?

“It’s safe to say ivory birds are not alone,” he said. “Someone who is relying on the land, or the ocean, to feed their families has done nothing to increase the amount of mercury in their food that they’re getting. But they are subjected to higher levels or contaminants because of what we do,” he said. “If the ivory gull is an indicator of the impact of industrialization, then I think it’s a canary in a coal mine.

“We need to recognize the impacts we have are sometimes invisible to our eyes, but the impacts are pretty significant when it comes to ecosystems and how they function. We really need to think about what is going on and start to pay attention to it.”

Reported by Paul Mayne, Western University